fix: correct source map columns for reused code that gets dedented#1433
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Kal-Aster wants to merge 2 commits into
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fix: correct source map columns for reused code that gets dedented#1433Kal-Aster wants to merge 2 commits into
Kal-Aster wants to merge 2 commits into
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Lines#getIndentAt never reports a negative indentation, so lines that already begin at column zero stay put when the surrounding lines are dedented. Mapping#indent nevertheless shifted every mapping by the full requested amount, which left the mappings of those lines pointing at the wrong columns, and made Lines#getSourceMap fail its sourceChar === targetChar invariant. Compare the indentation of the old and new Lines objects instead, so each mapping moves as far as its line really moved. Both skipFirstLine and noNegativeColumns become implicit in that comparison: line 1 keeps its indentation, so it never shifts, and clamping to zero is now part of computing the shift. Fixes benjamn#1402.
Reusing a parenthesized arrow function dedents it, while the lines of its body already begin at column zero and so stay where they are. Before the previous commit this threw Invariant failed instead of producing a source map.
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Fixes #1402.
DISCLAIMER
I don't know the opinion about AI usage in this project, however I don't know anything about how this works and this bug is sitting in here since a long time, so I used AI to produce a fix. I ensured that the code was matching the rest of the code in both style and structure, but other than that I just prompted the AI.
Follows an explanation of AI about the bug and its fix:
Lines#getIndentAtnever reports a negative indentation, so a line already at column zerostays put while the lines around it are dedented.
Mapping#indentshifted every mapping bythe full requested amount anyway, leaving those mappings pointing left of the text they
describe, which failed the
sourceChar === targetCharinvariant inLines#getSourceMap.It now derives the shift by comparing the indentation the old and new
Linesactuallyrender, so each mapping moves as far as its own line moved.
skipFirstLineandnoNegativeColumnsfall out of that comparison, makingMapping#indent27 lines shorter.Added a regression test that throws
Invariant failedwithout the fix.